An Intranet Private Branch (iPBX) is a telephony a solution where voice communications are effected over a Local Area Network (LAN) using Voice over IP (VoIP). FIG. 1 illustrates a plurality of IP devices such as phones 1A, 1B, 1C and 1D connected to a central server or iPBX 3 using a LAN 5. The iPBX 3 sets up voice connections between the phones over the LAN 5 (ie. subnet) in order to allow communication therebetween using Real-Time Transport Protocol (RTP) voice packets. The iPBX 3 also allows the phones to communicate over analog phone lines on the Public Switched Telephone Network (PSTN)
It is also known in the art to provide additional network access capabilities to IP phones such as analog line peripherals, Session Initiated Protocol (SIP) support or connection to wireless LAN capability, for example. Analog line peripheral 7 allows IP phone 1D to connect directly to the Public Switched Telephone Network (PSTN) in the event that the phone is unable to communicate with the iPBX 3 due to failure, software upgrade or a LAN infrastructure problem, as described, for example, in commonly-owned United States Patent Application published under 20040190685 on Sep. 30, 2004, and entitled HIGH AVAILABILITY TELEPHONE SET, the contents of which are incorporated herein by reference.
Currently, the only method for providing failover connections to the PSTN for all of the IP phones in a subnet is to provide each IP phone with an analog line peripheral 7, as shown in FIG. 2. Often, this is not a practical solution since the number of IP phones on a subnet may exceed 100. It is therefore desirable to reduce the number of analog line peripherals required for a subnet while maintaining a failover connection for each IP phone.